netdev - RE: [PATCHv2 6/6] net: fec: fix regression on i.MX28 introduced by rx

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Date:	Tue, 28 Oct 2014 11:14:15 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Lothar Waßmann' <LW@...O-electronics.de>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:	"David S. Miller" <davem@...emloft.net>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Frank Li <Frank.Li@...escale.com>,
	"Fabio Estevam" <fabio.estevam@...escale.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCHv2 6/6] net: fec: fix regression on i.MX28 introduced by
 rx_copybreak support

From:  Lothar Waßmann
> commit 1b7bde6d659d ("net: fec: implement rx_copybreak to improve rx performance")
> introduced a regression for i.MX28. The swap_buffer() function doing
> the endian conversion of the received data on i.MX28 may access memory
> beyond the actual packet size in the DMA buffer. fec_enet_copybreak()
> does not copy those bytes, so that the last bytes of a packet may be
> filled with invalid data after swapping.
> This will likely lead to checksum errors on received packets.
> E.g. when trying to mount an NFS rootfs:
> UDP: bad checksum. From 192.168.1.225:111 to 192.168.100.73:44662 ulen 36
> 
> Do the byte swapping and copying to the new skb in one go if
> necessary.
> 
> Signed-off-by: Lothar Wamann <LW@...O-electronics.de>
> ---
>  drivers/net/ethernet/freescale/fec_main.c |   25 +++++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
> index 404fb9d..b92324c 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -339,6 +339,18 @@ static void *swap_buffer(void *bufaddr, int len)
>  	return bufaddr;
>  }
> 
> +static void *swap_buffer2(void *dst_buf, void *src_buf, int len)
> +{
> +	int i;
> +	unsigned int *src = src_buf;
> +	unsigned int *dst = dst_buf;
> +
> +	for (i = 0; i < len; i += 4, src++, dst++)
> +		swab32s(src);
> +
> +	return dst_buf;
> +}
> +

Actually that is completely f*cked....

	David